Data from the Kepler Space Telescope has revealed the Kepler-90 system ties with our own for the most number of planets known to orbit a single star. The discovery of an eighth exoplanet, Kepler-90i, revolving around its Sun-like star located 2,545 light years away in the constellation of Draco, was achieved using artificial intelligence software programmed to detect the distinct light signature of planets passing in front of their parent star.
According to NASA, the discovery of Kepler-90i was the result of the work by researchers Christopher Shallue and Andrew Vanderburg, who used an artificial "neural network" to examine the 35,000 possible planetary signals returned by the unmanned Kepler spacecraft. Artificial intelligence has been used before to process the Kepler data, but by imitating the way neurons connect in the human brain, Shallue and Vandenberg were able to train the computer to seek out and identify weak transit signals that had previously been missed.
"In my spare time, I started googling for 'finding exoplanets with large data sets' and found out about the Kepler mission and the huge data set available," says Shallue, who is a senior software engineer with the Google AI research team. "Machine learning really shines in situations where there is so much data that humans can't search it for themselves."
The researchers used machine learning by training the neural network to identify transiting planets from 15,000 previously-vetted signals, which allowed the software to identify planets and eliminate false positives with a 96 percent accuracy. This made it possible for the team to examine 670 systems known to have multiple exoplanets on the assumption that these systems were most likely to show weak light curves of further planets.
"We got lots of false positives of planets, but also potentially more real planets," says Vanderburg. "It's like sifting through rocks to find jewels. If you have a finer sieve then you will catch more rocks but you might catch more jewels, as well."
If you're hoping to book a holiday on Kepler-90i, best think again. The closest planet to its parent star, Kepler-90i completes its orbit every 14.4 days and is a rocky planet a third larger than Earth with a surface temperature of 800° F (427° C). And though the Kepler-90 system has as many planets as our solar system, it's much more compact, with the farthest out, Kepler-90h, only as far from its star as Earth is from the Sun.
"The Kepler-90 star system is like a mini version of our solar system," says Vanderburg. "You have small planets inside and big planets outside, but everything is scrunched in much closer."
The findings will be published in The Astronomical Journal.
The video below shows how Kepler-90i was discovered.
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